The present invention relates to methods for forming micro-optical switch components, and more particularly to an integrated fiber optic switch.
The demand for high-speed data transmission has accelerated the development of optical networks. For a local area network and very short reach data links, high efficiency and low equipment/operational cost have become central issues for meeting market needs. Local networks have evolved to include the use of vertical-cavity surface-emitting lasers (VCSEL) and PIN photodetector (PD) as light transmitters and receivers, respectively, and use multimode fiber (MMF) as signal transport media. A VCSEL is a diode laser where the laser oscillation and output occur normal to the PIN junction plane. Such lasers are formed in a structure of semiconductor layers deposited on a semiconductor substrate, and emit light from a port in the surface of the structure. A VCSEL generates a much more symmetrical light beam than an edge-emitting laser. As a result, the light from the VCSEL can be coupled into the optical system of a laser printer or optical communication link more efficiently than the light from an edge-emitting laser. Low divergent circular output, single longitudinal mode operation, and high two-dimensional packaging density for arrays, make VCSELs attractive for applications such as optical recording, communications, and computing.
Parallel technology has been applied to VCSEL arrays, PD arrays and fiber ribbons. Specific electronic circuits for driving VCSELs, processing PDs output signals, as well as for implementing small factor connectors have gradually standardized transceivers for short range communications. However, deficiencies exist in dealing with giga-bit-per second level of transmission over reasonable distance with a single channel. These limitations occur from the integration of optoelectronic parts with electronic circuits. Current VCSEL-microlens array integration schemes utilize wire connectors in which the parasitic capacitance of the wire connection limits the data processing rate of the unit. As a result, size-sensitive applications, and chip level integration have been a focus in the development of VCSELs for telecommunication and data communication applications.
Application technologies for VCSELs, PDs and complimentary-metal-oxide-semiconductor (CMOS) electronic circuits are well known. However, the interconnections, both electrical and optical, are difficult due to the small physical size, specific geometry, and materials employed. The simultaneous achievement of both interconnect types creates additional difficulties due to interactions.
Existing approaches for integrated switches utilize flip-chip bonding to attach the VCSEL and detector array to a silicon chip. Light passes through vias etched on the silicon chip and is coupled to the fibers by a reflection mirror. Additionally, a co-planar design is utilized in which the n-contact of the VCSEL must be removed after bonding to leave a path for the top emitting laser. It is also possible to bond the n-contact to the substrate and then remove the substrate beyond the n-contact, resulting in bottom emitting. For other structures, many processing steps are required for electrical connection, etching, metal deposition, reflow and rinsing. Additional processing steps are necessary for the alignment and coupling of light into and out of fiber array. Existing designs have severe cost disadvantages. Therefore, a need has arisen for new optical switches with new fabrication methods to meet existing market needs.
In accordance with the present invention, a method for forming a small, low cost, integrated fiber optic switch is provided. The switch component is based upon VCSEL arrays and PD arrays, both coupled directly to an integrated circuit. The use of ink jet dispensing of polymers and solders create high quality optical and electrical interconnects to the active elements. Collimating and focusing polymer microlenses are printed directly onto the VCSEL arrays with photolithographic accuracy so that the light emitting from the VCSELs will directly couple into arrays of optical fibers. Collimating and focusing polymer microlenses are also utilized for coupling light from optical fibers into detector arrays. Ink jet dispensing of solders is utilized to electrically interconnect the active optical elements to the integrated circuit with minimal interconnect distance.
In accordance with the present invention, a method for forming a micro-optical switch component includes providing a semiconductor substrate having a surface. An opto-electronic device is integrated into the semiconductor substrate at a site. A pedestal of microlens material is formed on the semiconductor substrate surface at the site of the opto-electronic device. The pedestal extends from the semiconductor substrate surface and has a top surface spaced apart from the semiconductor substrate surface. A print head is provided and contains an optical fluid which is hardenable and capable of serving as a micro-optical element. The print head includes an orifice from which micro-droplets of the optical fluid are ejected in response to control signals. Optical fluid is deposited onto the top surface of the pedestal to thereby form a micro-optical element on the pedestal.